For the first time in recent memory, a chink emerged -- albeit small and perhaps temporary -- in Google's armor. It's U.S. search share declined slightly from 57.7 percent in November to 56.3 percent December, according to numbers released today by Nielsen Online. Here's a blog post on the November report.

In the same period, Microsoft got a boost with its MSN/Live Search going from about 12 percent of U.S. searches in November to 13.8 percent in December, which is where it stood in October.

Yahoo was essentially unchanged at 17.7 percent in December, compared with 17.9 percent in November.

Microsoft also saw the "stickiness" of its search engine improve.

Nielsen measures searches per searcher, an important indicator of how useful people are finding the various search engines. (If you like the results you're getting, you're likely to keep using the product, right?)

Microsoft saw its searches per searcher increase from 27.8 in November to 31.7 in December. Google's number fell from 40.8 to 37.9.

Of course, one month's data does not a trend make. But given the effort Microsoft is pouring into search and the lack of results it had seen until now -- and the fact that it's Friday -- this can be counted as a small victory.

We'll be looking for data to confirm this report from comScore and of course keeping an eye on what happens in January and beyond.